1. Field of the Invention
The present invention relates to a method, circuit and apparatus for compensation of operationally and/or environmentally caused maladjustments of laser resonant cavities in folded arrangement and employing a support construction for the resonator, which is provided as a preferably vertically disposed double T-profile section produced from relatively light materials.
2. Brief Description of the Background of the Invention Including Prior Art
Conventionally CO.sub.2 laser resonant cavities are constructed from expensive thermally stabilized invar constructions, where the lasers have a power range of up to 1000 watts and employ a slow flow of gas. In part even novel materials such as for example surperinvar are employed as construction materials. In addition, it has been attempted to employ massive marble blocks as a stable support for the optical components of a laser resonant cavity. These constructions meet in fact the optical requirements, but they are very expensive and have masses and dimensions which are much too large for industrial applications. In addition, such constructions make it appear that a further increase in the output power of a laser would not make economic sense. On the other hand the developed laser technologies have been extremely useful in industrial applications, in particular the application of CO.sub.2 lasers, such that stronger and stronger requirements are posed regarding the reduction of mass and volume. Fulfilling these requirements leads to new requirements regarding the laser resonant cavities and their thermal stabilization.
In order to reduce the construction length, folded path resonant cavities have been developed, which however are much more temperature sensitive compared with the above indicated resonant cavity constructions and which therefore again limit the possibilities of industrial applications. It has been attempted to balance this disadvantage by introduction of additional thermal stabilization provisions for the resonant cavity construction such as use of water, oil and climate insulation and control procedures. Temperature stabilization has been only partially achieved, that is as in the past with a reduction of the temperature range over which the apparatus can be employed. In addition, the steps described have resulted in an increase of mass and of volume and have thus also increased the costs.
In order to avoid these disadvantages it also has been proposed to employ a double T-profile section from light construction materials and using low-cost materials as a support construction for the laser resonator. However, such constructions have not been generally accepted so far since with the materials so employed, such as aluminum and steel sheet, even with a temperature variation of only one degree centigrade considerable maladjustments of the laser resonant cavity occur due to environmental and operational climate effects, such that the quality of the laser beam and the laser output power are degraded so far that a working and treatment of the material or structure to be machined or milled could not be assured under the quality requirements imposed. A shielding of such climatic influences or, respectively, temperature variations cannot be achieved with sufficient success by expensive insulation steps or by operational stabilizations such as stabilization of the cooling water temperature, stabilization of the fed in electric energy or the like. Thus it has to be concluded that the requirements necessarily to be imposed for the operation of such a laser regarding temperature stability can be achieved only under unacceptably high costs and appear therefore to be substantially uneconomical or, alternatively, they defeat or overcompensate the advantages conceptually achievable with the light construction method.